Antagonistic Microorganisms Research Articles

Fungal diversity and community composition of wheat rhizosphere and non-rhizosphere soils from three different agricultural production regions of South Africa

Understanding complex interactions among plant genotypes, environmental conditions and microbiome structure provides crucial information for sustainable farming practices towards disease control in agriculture. In this study, fungal diversity and composition in wheat rhizosphere and non-rhizosphere soils were investigated. Special emphasis was placed on pathogenic and beneficial genera. Wheat rhizosphere and non-rhizosphere soil from three different wheat growing regions were analyzed using Illumina high-throughput sequencing. The analysis showed a significant decline in the fungal diversity and richness from non-rhizosphere to rhizosphere soils. Ascomycota and Basidiomycota were the dominant fungal phyla detected in both rhizosphere and non-rhizosphere soils across the three test sites. Genera known to include wheat pathogens detected included Fusarium, Phoma and Colletotrichum genera while, beneficial groups included Trichoderma, Aureobasidium and Acaulospora. The presence of Fusarium was observed to be inversely proportional to that of Aureobasidium, a well-known antagonist of the Fusarium spp. This information could provide new opportunities to explore the potential of manipulating natural fungal antagonistic microorganisms for use in controlling soil-borne pathogenic fungi in wheat.

Inoculation with Streptomyces decreases vascular wilt of chickpea infected by Fusarium oxysporum f. sp. ciceri

Vascular wilt caused by Fusarium oxysporum f. sp. ciceri (FOC) is a disease that limits the yield of chickpea in Algeria. Biological control with antagonistic microorganisms is one of the alterna ves methods to ght this fungal disease. In this work, we tested an ac nomycete Streptomyces ACT2 against 03 isolates of FOC (FOC8, FOC13, FOC 15) in vivo on three varie es of chick- pea including a sensi ve variety (ILC-482) and two varie es moderately tole- rant (Col-27, PPC-25) in order to highlight its effect on the reduc on or suppression of this disease. The results obtained showed that the degree of suppression of the disease by ACT2 varies from one variety to another and from one FOC isolate to another. The maximum suppression of the disease was observed in the Col-27 variety. The ACT2 isolate showed higher levels of disease suppression in both the moderately sensi ve Col-27 (13.68%) and PPC- 25 (18.78%) varie es than the sensitive variety ILC-482 (8.76%). The Streptomyces (ACT2) can be used as a biological protector of chickpea infected by the pathogen Fusarium oxysporum f. sp. ciceri.

Ability of Trichoderma harzianum in carbon fiber and silica nano particles formulation to control Fusarium oxysporum in vitro

Basal rot disease caused by Fusarium oxysporum f. sp. cepae is one of the major diseases that cause yield loss on shallot. Utilization of biocontrol agents can be applied as an environmentally safe control method. The antagonistic microorganism that has the potency to control fusarial diseases is Trichoderma harzianum. A carrier is required in preparing a formulation of this antagonistic fungus as a biocontrol delivery system (BDS). Carbon fiber was proven suitable as a carrier of some antagonistic bacteria. A formulation can also be supplemented with plant micronutrient. Addition of silica nano particles (Si NPs.) in the formulation did not reduce the viability of the antagonistic bacteria. An experiment was carried out to determine the ability of T. harzianum in the formulation with carbon fiber and Si NPs. to suppress the in-vitro growth of F. oxysporum. The experiment was arranged in the completely randomized design with 5 treatments and 5 replications. The treatments were challenging F. oxysporum by T. harzianum in different composition of formulation on potato dextrose agar. The compositions consisted of T. harzianum + 0.5% Si NPs., T. harzianum + 1% Si NPs., T. harzianum + 0.5% Si NPs. + 5% carbon fiber, T. harzianum + 1% Si NPs. + 5% carbon fiber, and T. harzianum only (control). The results showed that each treatment with T. harzianum in the formulation of carbon fiber + various concentrations of Si NPs. was able to suppress the in vitro growth of F. oxysporum by 58.39-60.92%. The BDS with carbon fiber and Si Nps. did not significantly reduced the ability of T. harzianum to antagonize F. oxysporum. The control treatment of single T. harzianum caused the highest suppression on the growth of F. oxysporum, up to 60.93%..

Predominant Mycotoxins, Pathogenesis, Control Measures, and Detection Methods in Fermented Pastes.

Fermented pastes are some of the most popular traditional products in China. Many studies reported a strong possibility that fermented pastes promote exposure to mycotoxins, including aflatoxins, ochratoxins, and cereulide, which were proven to be carcinogenic and neurotoxic to humans. The primary mechanism of pathogenicity is by inhibiting protein synthesis and inducing oxidative stress using cytochrome P450 (CYP) enzymes. The level of mycotoxin production is dependent on the pre-harvest or post-harvest stage. It is possible to implement methods to control mycotoxins by using appropriate antagonistic microorganisms, such as Aspergillus niger, Lactobacillus plantarum, and Saccharomyces cerevisiae isolated from ordinary foods. Also, drying products as soon as possible to avoid condensation or moisture absorption in order to reduce the water activity to lower than 0.82 during storage is also effective. Furthermore, organic acid treatment during the soaking process reduces toxins by more than 90%. Some novel detection technologies based on magnetic adsorption, aptamer probes, and molecular-based methods were applied to rapidly and accurately detect mycotoxins in fermented pastes.

Use of yeasts from different environments for the control of Penicillium expansum on table grapes at storage temperature

A wide range of fresh fruits and vegetables is attacked by Penicillium species causing diseases during their postharvest handling. Many of these species are psychrotrophic and they are able to cause food spoilage at refrigeration temperature as happens with table grapes. After the harvest, grape bunches are stored inside boxes with SO2 generator pads to reduce the contamination with fungal conidia. However, SO2 residues are dangerous to people allergic to sulfites and they negatively affect the quality of fresh fruit. Biological control of phytopathogens with microbial antagonists naturally present on fruit surfaces could be helpful against postharvest diseases. The present study aimed to select native yeasts isolated from fermentation microenvironments and the surface of refrigerated grapes for their use in the biological control of P. expansum on table grapes stored in cold rooms. Non-pathogenic and pathogenic Penicillium species were isolated, and the four most aggressive pathogen isolates were identified as Penicillium expansum. Twenty yeast isolates identified as Aureobasidium pullulans, Cryptococcus magnus, Metschnikowia pulcherrima and Rhodotorula glutinis presented positive antagonistic activity against Penicillium expansum; they controlled the development of at least one of the fungi, significantly reducing the disease incidence. The results showed that three antagonistic yeasts (M. pulcherrima 22, 36 and 43) reduced the disease incidence and severity of all 4 P. expansum isolates. It was also found that the fruit surface is not the only source for isolation of biological control agents. Microenvironments with different stress conditions could be a promising source to isolate antagonistic microorganisms.

Taxonomic Characterization, and Secondary Metabolite Analysis of Streptomyces triticiradicis sp. nov.: A Novel Actinomycete with Antifungal Activity.

The rhizosphere, an important battleground between beneficial microbes and pathogens, is usually considered to be a good source for isolation of antagonistic microorganisms. In this study, a novel actinobacteria with broad-spectrum antifungal activity, designated strain NEAU-H2T, was isolated from the rhizosphere soil of wheat (Triticum aestivum L.). 16S rRNA gene sequence similarity studies showed that strain NEAU-H2T belonged to the genus Streptomyces, with high sequence similarities to Streptomyces rhizosphaerihabitans NBRC 109807T (98.8%), Streptomyces populi A249T (98.6%), and Streptomyces siamensis NBRC 108799T (98.6%). Phylogenetic analysis based on 16S rRNA, atpD, gyrB, recA, rpoB, and trpB gene sequences showed that the strain formed a stable clade with S. populi A249T. Morphological and chemotaxonomic characteristics of the strain coincided with members of the genus Streptomyces. A combination of DNA–DNA hybridization results and phenotypic properties indicated that the strain could be distinguished from the abovementioned strains. Thus, strain NEAU-H2T belongs to a novel species in the genus Streptomyces, for which the name Streptomyces triticiradicis sp. nov. is proposed. In addition, the metabolites isolated from cultures of strain NEAU-H2T were characterized by nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. One new compound and three known congeners were isolated. Further, genome analysis revealed that the strain harbored diverse biosynthetic potential, and one cluster showing 63% similarity to natamycin biosynthetic gene cluster may contribute to the antifungal activity. The type strain is NEAU-H2T (= CCTCC AA 2018031T = DSM 109825T).

Control of Aflatoxigenic Molds by Antagonistic Microorganisms: Inhibitory Behaviors, Bioactive Compounds, Related Mechanisms, and Influencing Factors.

Aflatoxin contamination has been causing great concern worldwide due to the major economic impact on crop production and their toxicological effects to human and animals. Contamination can occur in the field, during transportation, and also in storage. Post-harvest contamination usually derives from the pre-harvest infection of aflatoxigenic molds, especially aflatoxin-producing Aspergilli such as Aspergillus flavus and A. parasiticus. Many strategies preventing aflatoxigenic molds from entering food and feed chains have been reported, among which biological control is becoming one of the most praised strategies. The objective of this article is to review the biocontrol strategy for inhibiting the growth of and aflatoxin production by aflatoxigenic fungi. This review focuses on comparing inhibitory behaviors of different antagonistic microorganisms including various bacteria, fungi and yeasts. We also reviewed the bioactive compounds produced by microorganisms and the mechanisms leading to inhibition. The key factors influencing antifungal activities of antagonists are also discussed in this review.

The occurrence of antagonists microorganisms to phytopathogenic fungi in consideration of various tillages

The influence of different tillage methods (20-22 cm plowing) with applying nitrogen fertilizer and without it on the occurrence of antagonist microorganisms to phytopathogenic fungi Bipolaris sorokiniana was studied. Tillage with overturning soil (20-22 cm plowing) increased credibly (p<0.01) the frequency of occurrence of antagonist microorganisms in compare with No-till. The using nitrogen fertilizer (ammonium nitrate) didn’t affect the occurrence of antagonist microorganisms.

Selected isolates of Trichoderma gamsii induce different pathways of systemic resistance in maize upon Fusarium verticillioides challenge

The pink ear rot is one of the most damaging maize diseases, caused by the mycotoxigenic fungal pathogen, Fusarium verticillioides. The application of biological control agents, like antagonistic and/or resistance inducer microorganisms, is an option to reduce fungal infection and kernel contamination in a sustainable and environmentally friendly way. It is well known that Trichoderma species are non-pathogenic fungi able to antagonize plant pathogens and to induce systemic resistance in plants. The present work aimed to verify if Trichoderma spp., applied to maize kernels, affect the plant growth and induce systemic responses to F. verticillioides. Besides, the capability to reduce fumonisin concentration in liquid cultures was investigated. Two T. gamsii (IMO5 and B21), and one T. afroharzianum (B75) isolates, selected both for antagonism and for the ability to reduce root infections, significantly reduced the endophytic development of the stem-inoculated pathogen, compared to the control. The mechanisms of action appeared to be strain-specific, with IMO5 enhancing transcript levels of marker genes of Induced Systemic Resistance (ZmLOX10, ZmAOS, and ZmHPL) while B21 enhancing marker genes of Systemic Acquired Resistance (ZmPR1 and ZmPR5), as evinced by measuring their expression profiles in the leaves. Moreover, IMO5 promoted plant growth, while B21 was able to significantly reduce the fumonisin content in a liquid medium. The results of this work give new evidence that the seed application of T. gamsii is a promising tool for controlling F. verticillioides to be integrated with breeding and the adoption of good agricultural practices.

STUDI AWAL EMPAT ISOLAT BAKTERI ANTAGONIS TERHADAP JAMUR Colletotrichum gloeosporioides

Serangan penyakit antraknosa yang disebabkan oleh jamur Colletotrichum gloesporioides pada beberapa tanaman yang bernilai ekonomi tinggi sangat merugikan para petani. Cara konvensional yang banyak dimanfaatkan para petani untuk mengatasi permasalahan tersebut adalah dengan melakukan penyemprotan fungisida sintetik yang berdampak negatif terhadap konsumen dan lingkungan. Alternatif lain yang dibutuhkan untuk menggantikan peran fungisida sintetik tersebut adalah dengan menemukan mikroorganisme antagonis terhadap jamur C. gloesporioides yang kemudian dapat digunakan sebagai bahan biofungisida yang aman bagi kesehatan dan lingkungan. Empat isolat bakteri antagonis jamur C. gloeosporioides yaitu UBCR_12, UBCR_36, UBCF_01, dan UBCF_13 tengah dikembangkan sebagai bahan untuk pembuatan biofungisida. Sebagai tahap awal penelitian pengembangan terhadap keempat bakteri tersebut, dilakukan sejumlah pengujian untuk mengidentifikasi dan mendapatkan sejumlah informasi terkait karakter keempat isolat tersebut. Pengujian morfologi menunjukkan bahwa isolat UBCR_12 adalah , UBCR_36 adalah, UBCF_01 adalah, dan UBCF_13 adalah. Pengujian biokimia menunjukkan bahwa UBCR_12 adalah , UBCR_36 adalah, UBCF_01 adalah, dan UBCF_13 adalah. Sedangkan pengujian dengan molekuler melalui kloning gen 16S rRNA menunjukkan bahwa isolat UBCR_12 adalah Serratia plymuthica.

Effect of Soil Properties on the Spread of Heterobasidion Root Rot

Abstract The literature review focuses on the effect of forest soil properties on infection of coniferous trees and stumps by Heterobasidion spores and further growth of mycelium from tree to tree. Spread of the fungus is greater in alkaline soil. Forest plantations on former agricultural lands have an increased risk of infection, due to lack of antagonistic soil microorganisms. In Latvia, severe infection of spruce stands by Heterobasidion root rot has been observed on peat soils.

ESTRATEGIAS DE CONTROL BIOLÓGICO UTILIZADAS PARA EL MANEJO DE LA ANTRACNOSIS CAUSADA POR Colletotrichum gloeosporioides EN FRUTOS DE MANGO: UNA REVISIÓN SISTEMÁTICA

&lt;p&gt;The mango (&lt;em&gt;Mangifera indica&lt;/em&gt; L.) is one of the most produced tropical fruits in the world, however, during post-harvest it is affected by pathogens such as &lt;em&gt;Colletotrichum gloeosporioides&lt;/em&gt;, which causes mango anthracnose. Synthetic fungicides are generally used to control this disease, but prolonged use can cause health and environmental effects; Therefore, biological control emerges as an alternative for the management of this disease, given that it is considered an effective and safe technique. The objective of this study was to describe the biological control strategies used for the management of anthracnose caused by &lt;em&gt;C. gloeosporioides&lt;/em&gt; in mango fruits from a systematic review of the scientific literature. The ScienceDirect, Scopus and Scholar Google databases were used. It was found that the largest number of publications were made in 2013 and 2017, with Ataúlfo and Tommy Atkins as the most studied mango varieties and Mexico was the country with the highest number of articles reported. The most studied biological control mechanism was the effect of functional groups of microorganisms on mycelial growth and the highest percentages of inhibition were reported for this mechanism, although the greatest number of reports on control mechanisms were of the category of antagonistic microorganisms. It is concluded that knowledge about the mechanisms used to control anthracnose will allow adopting more effective, practical and reliable measures; thus, managing to maintain mango quality during the storage, distribution and marketing period.&lt;/p&gt;

Trichoderma harzianum: biocontrol to Rhizoctonia solani and biostimulation in Pachyphytum oviferum and Crassula falcata

In this study the possibility of using Trichoderma harzianum as a possible promoter of the growth of plants of Pachyphytum oviferum and Crassula falcata and in the biocontrol of Rhizoctonia solani was evaluated. The 2 experimental groups under cultivation were: 1) group without Trichoderma (CTRL), irrigated with water and previously fertilized substrate; 2) group with Trichoderma harzianum (TH) and fertilized substrate. The test showed a significant increase in the agronomic parameters analysed in plants treated with Trichoderma harzianum (TH). In fact, all plants treated with (TH) showed a significant increase in the number of leaves, plant height, vegetative and root weight, new shoots number, stem diameter, flowers and inflorescences number, flowering time. The use of Trichoderma harzianum can significantly influence photosynthesis and chlorophyll content in Pachyphytum oviferum and Crassula falcata and control the development of Rhizoctonia solani. The use of this antagonistic microorganism could therefore be a valid alternative for those growers who, during the cultivation cycle of ornamental and horticultural plants, pay attention to plant quality and respect for the environment, optimizing the use of fertilizers and reducing the application of plant protection products.

Defence compounds in pollen: why do they occur and how do they affect the ecology and evolution of bees?

Pollen plays two important roles in angiosperm reproduction, serving as a vehicle for the plant's male gametes, but also, in many species, as a lure for pollen-feeding animals. Despite being an important food source for many pollinators, pollen often contains compounds with known deterrent or toxic properties, as documented in a growing number of studies. Here we review these studies and discuss the role of pollen defensive compounds in the coevolutionary relationship between plants and bees, the preeminent consumers of pollen. Next, we evaluate three hypotheses that may explain the existence of defensive compounds in pollen. The pleiotropy hypothesis, which proposes that defensive compounds in pollen merely reflect physiological spillover from other plant tissues, is contradicted by evidence from several species. Although plants may experience selection to defend pollen against poor-quality pollinators, we also find only partial support for the protection-against-pollen-collection-hypothesis. Finally, pollen defences might protect pollen from colonisation by antagonistic microorganisms (antimicrobial hypothesis), although data to evaluate this idea are scarce. Further research on the effects of pollen defensive compounds on pollinators, pollen thieves, and pollen-colonising microbes will be needed to understand why many plants have chemically defended pollen, and the consequences of those defences for pollen consumers.

Potential of Biocontrol Agents in Plant Disease Control for Improving Food Safety

Plant disease control is mainly based on extraneous application of pesticides to improve agriculture productivity. However, only a part of applied pesticides is used for killing of pathogens and pests. Large part of applied pesticides remains either as residual pesticide or gets volatilized or leached resulting in ecological and environmental problems, and human health hazards. The increased consumer demands for safe food have invigorated research on development of safe and ecofriendly biopesticides. The use of microorganisms for biological control of pests is considered as a pragmatic approach which can drastically lessen the adverse outcomes of agrochemicals in soil. Rhizospheric microorganisms isolated from various crops produce different antagnostic compounds and inhibit the growth of various phytopathogens and insect pests. Moreover, in several plants, hormones like salicylic acid, jasmonic acid and ethylene contribute towards induction of both, systemic acquired as well as induced systemic resitance. In this article, antagonistic rhizosphere microorganisms have been explored for control of phytopathogens. Further, recent advances in field of biopesticides using rhizosphere microorganisms under field conditions is discussed for improvingcrop productivity in sustainable agriculture

Antagonismo de Trichoderma spp. vs hongos asociados a la marchitez de chile

&#x0D; En México se siembran más de 100 variedades de chile (Capsicum annuum L.), es un cultivo altamente redituable y representa una actividad económica de importancia nacional. Actualmente, enfrenta graves problemas fitosanitarios por la presencia de enfermedades como la marchitez del chile, causada por un complejo de patógenos de suelo. Para el control de estas enfermedades, se utilizan fungicidas tóxicos y residuales, que contaminan el ambiente e inducen resistencia genética en los fitopatógenos. Por ello, es necesario buscar alternativas de control para solucionar este problema, por tanto, el objetivo de este trabajo fue evaluar el efecto antagónico de Trichoderma spp., contra los agentes causales de marchitez en confrontaciones in vitro mediante cultivos duales. El estudio se llevó acabo en 2016, en la Universidad Intercultural de Estado de Puebla, Huehuetla, Puebla, México. Se evaluaron tres aislamientos de Trichoderma provenientes de la rizósferas de árboles de aguacate, T. viride, T. harzianum y T. asperellum y tres aislamientos de los fitopatógenos P. capsici, F. oxysporum y R. solani obtenidos de las raíces de plantas de chile con síntomas de la marchitez. Los aislamientos se caracterizaron morfológicamente para su identificación. Los tres hongos antagonistas presentaron alto porcentaje de inhibición, T. asperellum mostró el 88.25%, T. viride 87.22% y T. harzianum con 87.8%. En las condiciones del estudio, T. asperellum, T. viride y T. harzianum, resultaron microorganismos antagónicos eficientes contra los fitopatógenos. Se sugiere realizar evaluaciones de biocontrol con estos aislamientos en invernadero y a campo abierto.

Strategies for Rot Control of Soybean Sprouts.

Soybean sprouts are nutrient-rich, contain plentiful proteins, vitamin C, and minerals and are packed in small numbers after production. As soybean sprouts were mass produced in a factory, the occurrence of rotting in soybean sprouts has become a serious problem. To overcome these problems, many efforts have been made to provide healthy soybean sprouts in Korea. This paper reviewed the physicochemical techniques used for supplying water with antibacterial properties and the natural antimicrobial materials developed for soybean sprout cultivation. On the basis of this review, 11 of the antimicrobial agents and/or techniques currently used originated from mineral, non-metal ions, and metal ions, 4 from antagonistic microorganisms, 7 from agents originating from animals, 31 from medicinal and herbal plants, and 11 from physicochemical agents and/or techniques. In addition, these agents and/or techniques showed potential not only for the inhibition of spoilage and rot of soybean sprouts but also for the extension of product shelf life, the enhancement of taste and aroma, the enhancement of nutrition and functional components, growth promotion, and/or the reduction of production costs. Continuous scientific innovations and improved processing technology will aid in further advancements and improvements in this area. Therefore, this study offers useful insights suggesting direction for future research and provides information on the different anti-rotting agents and/or techniques for soybean sprouts developed to date, also as discussed in various patents.

Suppression of soil-borne plant pathogens in growing media amended with espresso spent coffee grounds as a carrier of Trichoderma spp.

Espresso spent coffee grounds (SCG) are a high-value organic waste material often reported as a suitable soil amendment in horticulture. The aim of the present work was to evaluate the suppressiveness characteristics of SCG by the analysis of antagonistic microorganisms colonizing SCG and by a bioassay with cress grown on peat amended with 10% SCG and infested with the damping off causal pathogens Sclerotinia sclerotiorum and Phytophthora nicotianae. Among culturable microorganisms, mesophilic bacteria were the main forms colonizing SCG followed by actinomycetes. Fungal species isolated from SCG were represented by Trichoderma atroviride and, at a lesser extent, T. citrinoviride and Aspergillus sp. In vitro assays revealed that sterilized SCG were able to strongly inhibit mycelial growth of both S. sclerotiorum and P. nicotianae. By contrast, T. atroviride representative isolates Ta3 and Ta4, isolated from SCG, were able to rapidly colonise sterilized SCG. This result indicates that this species is insensitive to antimicrobial compounds present in SCG and are probably involved in the mechanism of soilborne pathogen suppression. Both Trichoderma isolates were characterised for their antagonistic activity. In dual culture assays, T. atroviride Ta3 and Ta4 inhibited the mycelial growth of both S. sclerotiorum and P. nicotianae and produced toxic volatile and non-volatile metabolites, having complementary inhibitory effects on growth of the target pathogens. Results from the bioassay revealed that sterilized peat-SCG substrate significantly reduced damping-off of cress due to P. nicotianae but failed to suppress that caused by S. sclerotiorum. When the sterilized peat-SCG substrate was enriched with T. atroviride Ta3 and Ta4 a consistent decrease of damping off caused by the two pathogens was recorded. SCG was found to be a valuable source of nutrients and not phytotoxic on cress at 10% peat substitution rate, but decreased plant growth. Present results indicate that SCG, a suitable component of mixed-peat or fortified substrates, are capable to provide disease suppression and represents an optimal substrate to support growth and activity of antagonistic Trichoderma.

Mechanisms underlying the effect of commercial starter cultures and a native yeast on ochratoxin A production in meat products

Processed meat products are of worldwide importance, but they are highly prone to fungal and ochratoxin A (OTA) contamination. In previous studies, several Lactic Acid Bacteria (LAB) and yeasts have been tested as biocontrol agents against P. nordicum growth and OTA production in meat products, with promising results. However, A. westerdijkiae has been poorly studied for this matrix.The aim of this work was to evaluate in vitro the mechanisms underlying the effects of a commercial starter culture and of a meat-native Candida zeylanoides strain on the growth and OTA production of P. nordicum and A. westerdijkiae, by co-culture in ham and sausage-based media under different conditions.In ham medium, C. zeylanoides live cells, cell broth and diffused compounds significantly inhibited OTA production by P. nordicum, but live cells of the starter culture significantly increased it. For A. westerdijkiae strong and significant stimulation was observed by direct contact in both media.In conclusion, ochratoxigenic fungi do not all respond to antagonistic microorganisms in the same way. This study sheds some light on the mechanisms behind the different effects of microorganisms.

Antifungal, Plant Growth-Promoting, and Genomic Properties of an Endophytic Actinobacterium Streptomyces sp. NEAU-S7GS2.

Diseases caused by Sclerotinia sclerotiorum have caused severe losses of many economically important crops worldwide. Due to the long-term persistence of sclerotia in soil and the production of air-borne ascospores, synthetic fungicides play limited roles in controlling the diseases. The application of antagonistic microorganisms can effectively reduce the number of sclerotia and eventually eradicate S. sclerotiorum from soil, and therefore considerable interest has been focused on biological control. Streptomyces sp. NEAU-S7GS2 was isolated from the root of Glycine max and its rhizosphere soil. It showed significant inhibitory activity against the mycelial growth of S. sclerotiorum (99.1%) and completely inhibited sclerotia germination. Compared to the control, in the pot experiment the application of NEAU-S7GS2 not only demonstrated excellent potential to control sclerotinia stem rot of soybean with 77 and 38% decrease in disease incidence and disease index, respectively, but could promote the growth of soybean. The light microscopy and scanning electron microscopy showed that co-culture of NEAU-S7GS2 with S. sclerotiorum on potato dextrose agar could lead to contorted and fragmented mycelia of S. sclerotiorum, which was associated with the secretion of hydrolytic glucanase and cellulase and the production of active secondary metabolites by NEAU-S7GS2. The plant growth promoting activity of NEAU-S7GS2 was related to the solubilization of inorganic phosphate, and production of 1-aminocyclopropane-1-carboxylate (ACC) deaminase and indole acetic acid (IAA). To further explore the plant growth promoting and antifungal mechanisms, the complete genome of strain NEAU-S7GS2 was sequenced. Several genes associated with ammonia assimilation, phosphate solubilization and IAA synthesis, together with genes encoding ACC deaminase, glucanase and α-amylase, were identified. AntiSMASH analysis led to the identification of four gene clusters responsible for the biosynthesis of siderophores including desferrioxamine B and enterobactin. Moreover, the biosynthetic gene clusters of lydicamycins, phenazines, and a glycosylated polyol macrolide showing 88% gene similarity to PM100117/PM100118 were identified. These results suggested that strain NEAU-S7GS2 may be a potential biocontrol agent and biofertilizer used in agriculture.